1. Field of the Invention
The present invention relates to a compact fan motor incorporated in various electronic devices such as mobile phones, car navigation systems, camcorders, and personal computers, and to an electronic device comprising a compact fan motor.
2. Related Background of the Invention
A brushless fan motor is known as a conventional technology in this field. In this type of fan motor, a shaft is supported by a bearing provided in a housing and an impeller is fixed to a front end of the shaft. An annular magnet is fixed to a back side of the impeller. A circuit board is fixed to the housing, and a coil disposed opposite to the magnet and a Hall element for detecting magnetic poles of the magnet are mounted on the circuit board. The impeller rotates in one direction when power distribution to the coil is switched after magnetic pole detection by the Hall element (See Patent Document 1 and Patent Document 2).
[Patent Document 1] Japanese Patent Application Laid-Open No. Hei 8-223863
[Patent Document 2] Japanese Patent Application Laid-Open No. 2005-245172
With miniaturization of various electronic devices, miniaturization of fan motor incorporated in such an electronic device is also desired. In a conventional fan motor, a magnet is provided integrally in a boss portion of an impeller and an effective area in a diameter direction of a vane of the impeller is made smaller by an area occupied by the magnet. Particularly, if the impeller is made smaller with miniaturization of the fan motor, the boss portion is hard to miniaturize because of many constraints of the magnet fixed to the impeller in connection with the coil on the circuit board, resulting in the effective area in the diameter direction of the impeller likely to be made still smaller. Further, the circuit board fixed to the housing must also be made smaller with miniaturization of the fan motor, but miniaturization thereof is hard in consideration of arrangements of the Hall element and coil.
An object of the present invention is to provide a compact fan motor that facilitates further miniaturization while broadening an effective area of a vane of an impeller and electronic devices comprising a compact fan motor.